Electrical Engineering - Transformers - Discussion

Discussion :: Transformers - General Questions (Q.No.2)

2. 

The turns ratio required to match an 80 source to a 320 load is

[A]. 80
[B]. 20
[C]. 4
[D]. 2

Answer: Option D

Explanation:

No answer description available for this question.

Jeykishan Kumar.K said: (Dec 14, 2010)  
Turn ratio will be proportion to square root of load.

Jen said: (Jan 19, 2011)  
Turns ratio2 = load impedance/source impedance

=2

Anirudhya said: (Jan 21, 2011)  
v1 I1=v2 I2
v1*v1/r1=v2*v2/r2
sq of (v1/v2)=r2/r1
sq of (1/k)=r2/r1=4
1/k=2------this is turns ratio
k=1/2-----this is transformation ratio
bcoz--n2/n1==transformation ratio
and
n1/n2==turns ratio

Vinay Kumar said: (Jan 25, 2011)  
Turn ratio will be proportion to square root of load.

Jegan said: (Mar 9, 2011)  
sq of(v1/v2)=r1/r2

Rajneesh said: (Mar 21, 2011)  
Turns ratio=(n2/n1)^1/2

Pruthibiraj Gouda said: (May 11, 2011)  
Here r1=80ohm, r2=320 ohm
we know v2/v1=i1/i2
v2/v1=v1/r1*r2/v2
=> k=(v1/v2)*(r2/r1)
=> k=1/k*(320/80)
=>K sq=4
k=2
Ans=2

Kallan said: (May 30, 2011)  
N2/N1=320/80=4

turns ratio= sq rt(n2/n1)=2

T.M.Eswar said: (Jun 7, 2011)  
I wants that why the frequency is constant for the transformers?

Saminathan said: (Jun 18, 2011)  
2T = load/source
2T = 320/80
T = 4/2
T=2

Azagu said: (Aug 7, 2011)  
Here frequency not be changed. Otherwise it just transmitted.

Siva said: (Sep 13, 2011)  
In transformers we use the 50hz, because of how much of load is given it will be operated at the same frequency so that we use the constant.

Zeeshan said: (Oct 14, 2011)  
If the above statment true that turn ratio is equal to load /source then answer comes 2.

Raju said: (Oct 30, 2011)  
Somebody told turns ratio equal to sqrt of the load. Is it correct or not ?

Relish said: (Nov 6, 2011)  
Turns ratio=a(n2/n1a)
Therefor R2=a^2*R1
a^2=R2/R1=4
a=2

Soujanya said: (Nov 13, 2011)  
What kallan said is right and less time consuming as wel as easy to remember.

Satya said: (Dec 15, 2011)  
As in a transformer input power = output power i.e. energy is transformed, v1^2 / z1 = v2^2 /z2. hence turns ratio = sqrt(z2/z1)

Bhabani Shankar Behera said: (Jan 12, 2012)  
I am satisfy with Pruthiwi Raj answer.

Shajeer said: (Jan 16, 2012)  
Turns Ratio = sqrt.(r2/r1)
= sqrt (320/80)
= sqrt (4)
= 2

Viji said: (Feb 21, 2012)  
sqrt(v1/v2)=r1/r2;
so,k=2

Md.Mofiz said: (Apr 9, 2012)  
Why the tranformer rating in kva?

Naresh said: (Apr 11, 2012)  
Is this process aplicable for all turns ratio problems?

Siva said: (Apr 25, 2012)  
Transformer rating is in kVA because Cu loss depends on only voltage and current and it is independent of power factor.

Palivela Varaprasad said: (Apr 29, 2012)  
v1xi1=v2i2
v1=cxn1
v2=cxn2
i1=v1/r1
i2=v2/r2
so
(n2/n1)2=(r2/r1)
Hence turns ratio n2/n1=root(4)=2

Dillip Kumar Dehury said: (May 6, 2012)  
Is any technique to know the KVA rating of transformer without nameplate?

Dillip Kumar Dehury said: (May 6, 2012)  
Why the iron loss is neglected during cu.loss test?

Siri said: (May 23, 2012)  
Cu losses does not depends on voltage, iron losses depends on voltage and Cu losses depends on current moreover power factor of t/f depends on load hence rated in kva where as in motors power factor depends only on construction hence rated in kw.

Navdeep Saini said: (May 29, 2012)  
Power is constant in both sides
I1sq*R1=I2sq*R2
Turn ratio=I1/I2=sqroot(R2/R1)=2

Venkatesh S said: (Jun 1, 2012)  
In question we understood that we convert the 320 ohm resistance in secondary as 80 ohm in the primary side (means source side). r'2 is 80, r2 is 320. Turns ratio is K.

r'2= (r2/K^2).
So that k=sqrt of (320/80).
K=2.

Keerthi said: (Jul 26, 2012)  
The Turns Ratio is always proportional to the square root of the load.

Uma said: (Sep 5, 2012)  
Turns ratio is directly proportional to square root of load impedance to source impedance i.e., here, sq root of 320/80=2.

Anil Kumar said: (Oct 20, 2012)  
As we know that V2/V1 = N2/N1 = I1/I2 = k.
So, V2/V1 = (V1/R1)*(R2/V2) = k.
=> (V2/V1)2 = R2/R1 = k.

Therefore, turns ratio(k) = sq. root of (R2/R1)
= sq. root of (320/80)
= 2.

Ashok Wath said: (Dec 23, 2012)  
N1/N2=V1/V2=I2/I1=K

Ajit Kumar said: (Feb 1, 2013)  
Why transformer can not work on DC?

Dr.G.Suresh Babu said: (Feb 18, 2013)  
Transformer works on the principle of Faradays Laws of Electro Magnetic Induction; with mutual Induction concept.

By Ohms Law ;current I = V/Z.
V =supply voltage- bak EMF.

Impedence Z =R+jX.
Reactance X =2 Pi f L.

We know that incase of DC supply,frequency f is zero;no induced EMF because there is no change of flux with DC(Induced EMF e= N dq/dt;).

Current I =(supply voltage-back EMF)/R=j+ X.

Here, numerator increases(back EMF is Zero) and denominator decreases(as X=0 and R is very less);consequently I increases to a dangerous level leading to burning of winding's if it is not properly fused.

Hence DC supply should not be connected to Transformer ; in-case connected a mechanism should be made to switch ON and OFF frequently(like SCR).

Gopinadh Puvvada said: (Feb 18, 2013)  
Assuming the transformer to be ideal,as losses in primary and secondary are equal.

(I1)^2/R1=(I2)^2/R2.

(I1/I2)^2=R2/R1.

I1/I2=SQRT(320/80).

I1/I2=2.

So the answer is 2.

Paban said: (Mar 21, 2013)  
We know in ideal Transformer v2/v1 = i1/i2 = k.

v2/v1 = (v1/r1)*(r2/v2).

(v2/v1)^2 = r2/r1.

After calculation result is 2.

Uday said: (Jun 3, 2013)  
What is converter transformer?

Abhijeet said: (Aug 22, 2013)  
What is the turns ratio the ratio of transformer needed to match 160 ohm load?

Pradip Pawar said: (Sep 25, 2013)  
Turn ratio = square root of load impedance upon source impedance.

Donfila said: (Nov 20, 2013)  
Copper losses are current square*resistance losses. Or winding losses. {I*I*R}.

Sarath said: (Nov 30, 2013)  
The impedance or resistance wrt both primary and secondary must be same which implies Z01 = Z02.

Where Z01 = Z1+(Z2/k^2).
Z02 = Z2+(Z1*k^2).

Solving the above equations I got '1' which isn't the answer.

Is it the correct approach ?

Engr. Mamoona Akbar said: (Jan 17, 2014)  
Turn ratio*2 = load impedance/source impedance.

Ranjeet Singh said: (Jan 21, 2014)  
v2/v1 = i1/i2.

= v1/r1*r2/v2.

(v2/v1)^2 = r2/r1.

(k)^2 = r2/r1.

k^2 = 320/80.

k^2 = 4 .

k = 2.

Ramm said: (Jan 25, 2014)  
Transformer rating is KVA, because iron&Cu losses depending upon the voltage and current only. Then not depending in the pf so its calls kva only.

Gursewak Singh said: (Mar 2, 2014)  
Turns Ratio = sqrt(r2/r1).
= sqrt (320/80).
= sqrt (4).
= 2.

Prakash said: (Mar 9, 2014)  
What is turns ratio? please explain.

Arun Kumar Raju C said: (Apr 4, 2014)  
The turns ratio of a transformer is defined as the number of turns on its secondary divided by the number of turns on its primary.

Akash.Bhure said: (Apr 30, 2014)  
Source resistance(R1) = 80 ohms.

Load resistance(R2) = 320 ohms.

R1 = R2/K^2.
80 = 320/K^2.
K^2 = 320/80 = 4.
K = sqrt(4) = 2.

Saranya said: (May 18, 2014)  
Single phase transformer 50hz 200 kva 11kv/230v test results: no load test: input = 1600watts short circuit test : 2600 watts calculate all day efficiency duty cycle 160kw 0.8 pf 8 hr 100kw unity pf 6hr remaining hrs no load.

Krishnakant said: (May 29, 2014)  
Numerical solution of single and three phase transformer.

Krishna said: (May 30, 2014)  
What is the relation the number of turns and the resistance?

Prudhvi Raj said: (Jun 28, 2014)  
Source side will be taken as primary then r1=80 and we have to match to secondary(loadside) given that it is 320 ie r1'=320.

Actually we know that whenever primary referred to secondary,
r1'=ksquare*r1.

So here,

ksquare*r1 = 320 that implies that,

ksquare = 320/r1=320/80=4.

i.e., ksquare = 4 then k=2.

Here k = tranaformation ratio.

Rpnagaraj said: (Aug 1, 2014)  
Because the impedances is the square of the turns ratio.

Shivendra said: (Sep 29, 2014)  
What is MOG protection in transformer?

Sharjeel said: (Nov 1, 2014)  
(Turns ratio)*2 = load impedance/source impedance.

Hari said: (Nov 17, 2014)  
Square root of Load impedance/source impedance.

Then answer is 4.

Ramakrishna18893 said: (Dec 1, 2014)  
Source belongs to primary winding where as load belongs to secondary winding. So in order to match or transfer impedance from primary side to secondary, k^2 (turns ratio) should be multiplied with primary impedance, then it will be equated with secondary impedance (matching is to obtain maximum power transfer). This is as illustrated.

80*k^2 = 320.
k^2 = 4.
k = 2.

In case transfer from secondary to primary, secondary impedance must be multiplied with 1/k^2. Equate it to primary impedance for matching. Same result will be obtained.

Sad said: (Dec 6, 2014)  
What is resistance please answer?

Kalidhas said: (Jan 1, 2015)  
What are things/Parameters are required to sizing the Distribution Transformers?

Ashu said: (Jan 14, 2015)  
What is the actual formula for turns ratio is it K=N1/N2 OR K=N2/N1 & what is transformation ration?

Rajesh Kanna said: (Jan 31, 2015)  
What is the meaning of unbalancing?

Saheb said: (Feb 11, 2015)  
R(hv) = K^2*R(lv).

[v2/v1 = k,i2*r2/i1*r1 = k, R(hv)/R(lv) = k^2; k = 2; r2/r1 = k^2].

Krishnakumar said: (Jun 3, 2015)  
During current loss test (short circuit) we had applied rated current of the transformer. Transformer reaches its rated current at some voltage. It is very low current loss only depend on voltage. So it is negligible.

Rangaswamy M.D said: (Jul 13, 2015)  
v2/v1 = i1/i2.
= v1/r1*r2/v2.
(v2/v1)^2 = r2/r1.

(k)^2 = r2/r1.
k^2 = 320/80.
k^2 = 4 .
k = 2.

Pal said: (Aug 4, 2015)  
N(s)/N(p) = E(S)/E(p)-1.

I(p) N(p) = I(s) N(p).

E(P) N(P) / R(P) = E(S) N(S)/R(S)-2.

From 1 and 2.

Sq (N(S)/N(P)) = R(s)/R(p).

Reshma said: (Sep 3, 2015)  
I m not satisfy this answer.

Turn ratio = E1/E2 =V1/V2 =N1/N2=1/k.

Gautam said: (Jan 18, 2016)  
Clearly given in question that:

Primary or source resistance R1 = 80 ohm.

Secondary resistance R2 = 320.

We know that:

Transformation ratio k = N1/N2 = V1/V2 = R2/R1 = I2/I1.

SO K = 320/80 = 4 is correct answer.

Chandrashekar said: (Feb 26, 2016)  
320 = n^2*80.

n^2 = 320/80 = 4.

n = 2.

Hanumantha Hk said: (Mar 5, 2016)  
Above all guys discussed ok but there is a mistake in that !

Turns ratio(n) = N1/N2 =V1/V2 = I2/I1.
Same Transformer ratio is (K) = 1/n.

Means V2/V1 = N2/N1 = I1/I2 = K.

The question is Turns Ratio ?
V1*I1=V2*I2.
(v1)^2/R1= (V2)^2/R2.
So (V1/V2)^2=R1/R2.

Turns ratio n = (N1/N2)^2=R1/R2=80/320=1/4.

When we make sqrt it will come = 1/2.

What you guys are saying the above solution ?

Amjad Moawia said: (May 1, 2016)  
No! @Hanumantha Hk.

The correct law is : vs/sp = NS/NP = IP/IS.

Please, revise once again.

Sudha said: (Jun 5, 2016)  
Can anybody solve this problem in a simple way?

Nidu said: (Jul 20, 2016)  
Sqr(Np/Ns) = Zp/Zs,

Because turns ratio is Np/Ns not Ns/Np.

Yash said: (Oct 11, 2016)  
Is any technique to know the KVA rating of the transformer without nameplate?

Haji Bilal said: (Nov 10, 2016)  
Hello, @Yash.

It should require to measure current and voltage of transformer from the secondary side. Then you will able to know KVA rating of the transformer!

K.Gopala Krishna said: (Dec 13, 2016)  
Here the value is in ohms.
i.e resistive
It will be more in winding.
n2/n1 = k,
320/80 = k,
= 4.

K.Gopalakrishna said: (Dec 13, 2016)  
Transformation ratio k = n2/n1.
Here the given value is in ohms i.e resistive.
That will be more in the winding.
i.e 320/8 = 4.

Prafulla said: (Mar 29, 2017)  
If primary Resistance transfer to the secondary winding. Then,
R2=K^2 R1.
320=K^2 80,
K^2=320/80 = 4.
K= √4 = 2.

Mb Sharon said: (Jun 28, 2017)  
The National Instructional Media Institute (NIMI) for Industrial Traning book.

Np/Ns=Zp/Zs.
Where,
Np=No of turns in the primary.
Ns=No of turns in the secondary.
Zp=primary impedance or (source).
Zs=secondary impedance or (load).
Sol; Source Z=80 ohm.
Load Z =320ohm.
Zp/Zs=80/320.
Turns Ratio =1:2 answer= 2.
1:2 Turns ratio match the 80 ohm source impedance to a 320 ohm load.

Surinder Rajput said: (Jul 5, 2017)  
Here is the little formula for impedance VS turns.
a= Turns Ratio, (Np/Ns)=Square Root of (Zp/Zs),
Square root of (380/20)=4/1,
Square root of (4/1)=2,
So 2.

Hemant said: (Aug 17, 2017)  
Can anyone give formula derivation for showing turns ratio in terms of resistance?

Dorsing said: (Oct 12, 2017)  
Given that,

R1=80 ohm
R2=320 ohm
Transformer Ratio,
K = N1/N2 = V1/V2=R2/R1=I2/I1.
K=R2/R1.
= 320/80=4.

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Harsha said: (Nov 25, 2017)  
If √(n2/n1) is turns ratio then what is n2/n1?

Mallikarjun Bhirade said: (Dec 10, 2017)  
Explanation:- Given Data, R1=80 Ohms, R2=320 Ohms, We have, R2/R1=K^2
Where, K=Transformation Ratio

Now, K^2=320/80=4 => K=√(4)=2
But, Turns Ratio = 1/K, Now, Turns Ratio = 1/2 =0.5 only!

Jh71Pa said: (Jan 29, 2018)  
Is it 2:1 or 1:2? Please tell me clearly.

B Shirisha said: (Jan 30, 2018)  
Load impedance ÷ source impedance.

Ramesh Vankudothu said: (Jul 2, 2018)  
K2: R2%R1
K2: 320%80
K = √4 => i.e 2.

Zoodee said: (Oct 6, 2018)  
It should be 1/2.

Rakesh said: (Mar 6, 2019)  
Turn ratio = √(R2/R1).
= √(360/80),
= √4,
= 2.

Jems said: (Mar 13, 2019)  
Thanks all for explaining.

Adarsh P K said: (Dec 23, 2019)  
Turns ratio = square root(Zs/Zp).

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